Multitube blood sampler

ABSTRACT

A multitube blood sampler of a type which uses two, three or more evacuated sample tubes of the type which are closed by rubber stoppers. The sampler combines a retainer which holds the sample tubes and a head fastened onto the front of the retainer which carries a forwardly projecting cannula and rearwardly projecting insert needles. The insert needles, within the retainer, pierce the rubber stoppers of the tubes. The unit is completed by a branched passageway within the head which connects the cannula to the insert needles so that when the cannula is inserted into the vein of a patient and the insert needles inserted into the several tubes, all of the tubes will be filled with a blood sample. The head carrying the cannula and insert needles is separable from the retainer and preferably, is provided as a throwaway unit once it has been used.

United States Patent 1 1 Inventor m Whimm 3,405,706 10/1968 Cinqualbre... 128/2 R0 808 130 610 Highway 86, Castle 3,469,578 9/1969 Bierman 128/214 RMIQCOIO- 80104 3,494,351 2/1970 Horn .1 l28/276 [2!] Appl. No. 759,002 [22] Filed Sept, 11, 1968 Pr1mary ExammerWarner H. Camp Patented Sept. 14, 1971 Attorne vVan Valkenburgh and Lowe [54] MULTn-UBE BLOOD SAMPLER ABSTRACT: A multitube blood sampler of a type which uses 13 Cl i 14 D i Figs two, three or more evacuated sample tubes of the type whlch are closed by rubber stoppers. The sampler combines a [52] U.S.Cl [28/2, retainer hi h h ld the sample tubes and a head fastened 128/276 onto the front of the retainer which carries a forwardly pro- [51] Int. Cl. A6lb 5/10, j gi cannula and rearwardly projecting insert needles. The A611 U00 insert needles, within the retainer, pierce the rubber stoppers {50] Field of Search 128/2, 214, f h b Th i i completed by a branched passageway 215. 216, 221. 214.2. 276; 220/60; 128/2 14.2, 2 within the head which connects the cannula to the insert needles so that when the cannula is inserted into the vein of a pa- [56] References cued tient and the insert needles inserted into the several tubes, all UNITED STATES PATENTS of the tubes will be filled with a blood sample. The head carry- 320,8l4 6/1885 Pollard 220/60 ing the cannula and insert needles is separable from the 3,208,620 9/ I965 Herdering 220/60 X retainer and preferably, is provided as a throwaway unit once 3,382,865 5/1968 Worrall, .lr. 128/2 it has been used.

PATENIED SEP 1 41971 SHEET 1 BF 2 INVENTOR. gory L. Whifacre WW/ZQ AT TORNE YS MULTITUBE BLOOD SAMPLER This invention relates to blood-sampling devices, and more particularly to blood-sampling devices which use evacuated sample tubes for receiving blood. The present invention provides an improved blood sampler which holds a plurality of such evacuated sample tubes.

The present methods of blood sampling in most hospitals and clinics throughout the country involve the use of evacuated tubes which are closed by soft rubber stoppers. Such a sample tube is fitted into a cylindrical retainer having a cannula projecting from its end. The base of the cannula includes a needle extension which lies within the retainer. Thus, whenever the cannula is inserted into a patients vein and the needle extension within the retainer is pushed into and through the stopper to break the vacuum, blood will flow from the vein and into the tube, the flow being enhanced by the vacuum to rapidly fill the tube. The tube is then removed from the retainer and the stopper again seals the tube as the needle is removed.

Should it be necessary to draw several samples of blood, the sample tube will be removed from the retainer, but the retainer will not be removed from the patient, and another sample tube will be inserted into the retainer and filled in the same manner. Additional sample tubes will be filled in the same way if necessary. While this system is far superior to, and has practically replaced the drawing of blood with a hypodermic syringe, it nevertheless has certain disadvantages when more than one sample is required. The obtaining of such blood samples in this sequential manner is time consuming, prolonging the discomfort and sometimes pain to the patient. Moreover, blood will often flow through the cannula when the tubes are being changed, and this lost blood can soil clothing and generally create a mess.

The problems created by the need for multiple blood samples can become very serious in hospitals and special care clinics, where two or more blood samples are required each time a patients blood is drawn. For example, in the Swedish Hospital in Denver, Colorado, a check indicated that in more than 90 percent of the cases where blood was drawn, two or more samples were required each time blood was drawn.

It follows that there is a real and definite need for improvements in blood sampling devices where it is necessary to draw more than one sample, and especially for a blood sampler which can reduce the time interval between the drawing of successive blood samples and also eliminate the problems created by blood lost between samples.

The present invention was conceived and developed with such a need in view, and the invention comprises, in essence, a multitube blood sampler having a single, outwardly projecting cannula for insertion into a patients vein, but a plurality of insert needles for insertion into tube stoppers. In use, the proper number of tubes are placed in the sampler and connected with the insert needles so that all of the tubes may be filled either simultaneously or sequentially without removing any from the retainer. Thus, when the tubes are filled, the retainer is removed from the patient and the blood drawing operation is completed.

It follows that an object of the invention is to provide a novel and improved blood sampler for a plurality of tubes, which reduces the blood-drawing time to a minimum whenever more than one sample is required, and at the same time, minimizes the discomfort experienced by the patient.

Another object of the invention is to provide a novel and improved multitube blood sampler which avoids the necessity of leaving the cannula in a patients vein after a sample tube is filled and removed, and thereby eliminates the mess which is sometimes caused by blood loss when sample tubes are being changed.

Another objedt of the invention is to provide a novel and improved multitube blood sampler which includes a simplified construction of a cannula head for a plurality of tubes, which is adapted to be quickly and easily fastened onto and subsequently disconnected from the sampler, and which may be provided as a sealed, completely sterile, low-cost, throwaway unit, once it has been used.

Another object of this invention is to provide a novel and improved multitube blood sampler which is especially suitable for being manufactured as either a two-tube, or three-tube unit, to cope with most demands for blood sampling, but may also be manufactured as a unit capable of using four or more tubes.

Other objects of the invention are to provide a novel and improved multitube blood sampler which is neat, economical and reliable, and which involves no special techniques and is used in substantially the same manner as single-tube blood samplers are presently being used.

With the foregoing and other objects in view, all of which more fully hereinafter appear, my invention comprises certain constructions, combinations and arrangements of parts and elements as hereinafter described, defined in the appended claims and illustrated in preferred embodiments in the accompanying drawings, in which:

FIG. 1 is a perspective view showing a two-tube sampler having its cannula in a patients forearm for drawing blood from the patient.

FIG. 2 is a longitudinal sectional plan view of the blood sampler shown at FIG. 1, as taken substantially from the indicated line 22 at FIG. 1, and with a broken line outline indicating a base which may be used to facilitate holding the two tubes together.

FIG. 3 is an isometric front end view of the sampler per se, but with the cannula head being separated from the tube retainer.

FIG. 4 is an isometric rear end view of the sampler per se, but with the cannula head being separated from the tube retainer.

FIG. 5 is a fragmentary detail view of a corner of the tube retainer, as taken from the indicated arrow 5 at FIG. 3, but on an enlarged scale, and with a resilient portion of the retainer being moved as to a position to effect a release of the cannula head from the retainer.

FIG. 6 is a bottom view of the cannula head, as taken from the indicated arrow 6 at FIG. 3, but on an enlarged scale.

FIG. 7 is a sectional view, as taken from the indicated line 77 at FIG. 6.

FIG. 8 is a sectional view, as taken from the indicated line 8-8 at FIG. 6.

FIG. 9 is a sectional view, as taken from the indicated line 99 at FIG. 6.

FIG. 10 is a fragmentary sectional portion, as taken from the indicated line 10-10 at FIG. 7, but on a further enlarged scale.

FIG. 11 is a plan view of an alternate construction of a three-tube blood sampler.

FIG. 12 is a transverse sectional view, as taken substantially from the indicated line 1212 at FIG. 11, and with broken lines indicating portions hidden from view, and also the manner in which the retainer is flexed to remove the head from the retainer.

FIG. 13 is a fragmentary sectional detail, as taken from the indicated line 1313 at FIG. 12, but on an enlarged scale.

FIG. 14 is an isometric view similar to FIG. 3, showing a modified form of a two-tube retainer.

Referring more particularly to the drawing, the two-tube blood sampler shown at FIGS. I to 10 is a somewhat flat, cuplike unit which is rectangular in plan and generally oval in cross section. It is formed as two components, including a retainer R adapted to hold the two sample tubes T. A cannula head H, attached to one end of the retainer, carries the cannula C and two tubular insert needles N which lie within the retainer. To facilitate the description of these components, the head H will be designated as being at the forward end of the sampler and thus designated, the cannula C extends forwardly from the front wall of this transversely disposed head, at the longitudinal center plane of symmetry of the unit. The cannula is also adjacent to the bottom edge of the head, that is, the bottom or undersurface of the unit which lies upon the patients arm as when asample is being taken, as illustrated at FIG. 1.

Each sample tube T is a conventional, standardized unit formed as an evacuated cylindrical test tube closed at its mouth by a comparatively thick, soft rubber stopper 2]! which holds the vacuum within it. The tube may contain selected reagents for specific tests and the rubber stoppers are usually color coded when reagents are used. These tubes are all the same size and will fit any standard sampler. The manner in which they are used is standardized. For example, a conventional blood-drawing operation is initiated by inserting the insert needle within the sampler part way into the stopper 21 and at a depth which will not break the vacuum within the tube. After the cannula is inserted into a patients vein, the insert needle is pushed through the stopper to provide communication from the vein to the interior of the tube so that a blood flow into the tube may commence which is facilitated by the vacuum within the tube. This basic procedure is not modified by the present invention as will appear.

In the present invention, the fiat, tube-retainer R is preferably manufactured as a unitary member of any transparent, rigid but resilient synthetic resin such as a selected acrylic polyethylene, vinyl, butadiene styrene or high-impact polystyrene, or any other type which may be manufactured at low unit cost by injection molding or other similar process. This retainer is symmetrical from each side of its longitudinal center plane and two longitudinally disposed passageways 24 extend through this retainer. Each passageway has a diameter sufficient to easily receive a standard sampler tube T and while the passageways are illustrated as being separated by a center wall 25, it is to be noted that a portion of this wall may be omitted as in the manner illustrated at FIG. 14. The sidewalls 26 of this retainer are rounded or are cylindrical in form. The bottom surface 27 is preferably arched slightly to better fit upon a patients arm, and to enhance the appearance of the unit, the top surface 28 may be crowned upwardly slightly to compliment the arched bottom surface.

The length of this retainer R is such as to permit a sample tube to be inserted from the rear of the retainer a little more than halfway into a retainer passageway when the stopper 21 contacts the end of an insert needle N and this needle is inserted into the stopper. The retainer R is necessarily transparent to permit a technician to watch the insertion of the stopper end of a sample tube T into a needle N. To facilitate a proper preinsertion where the needle end does not extend through the stopper, but only partially into the stopper as illustrated at FIG. 2, a limit line 29 may be provided across the top of the unit, the same as is provided in conventional single-tube retainers. Also, a finger flange 30 is provided at each side of the rear end of the retainer to facilitate a technician in gripping it to push tubes into place beyond the line 29 after the cannula has been inserted into the vein of a patient.

This retainer R is completed by a means for connecting with the cannula head H at the forward end of the unit. In the unit illustrated at FIGS. 2 to 5, the cannula head connector includes a socket 31 at each sidewall 26 near the front end thereof, which is adapted to receive mating, inturned lugs on the head as hereinafter described. In order to permit connecting with these fixed lugs, the sidewall at one side of the retainer is formed as a flexible strip 32 between longitudinal, spaced slits 33 at each side of the socket. These slits extend from the forward end of the retainer and into the body of the retainer to permit the forward end of the strip to be flexed inwardly by finger pressure a distance sufficient to release it from a lug, as to the position illustrated at FIG. 5. To facilitate pushing this strip to its flexed position, a wedged-shaped finger tab 34 may be formed upon this strip as illustrated.

The cannula head H is essentially a flat member oriented transversely when connected to the front end of the retainer. It consists of two parts which are joined together as will be hereinafter described. The parts are preferably manufactured by injection molding a synthetic resin plastic material as rigid,

but not necessarily transparent members. The plastic selected for the head H must also be capable of bonding to hold the metal cannula and insert needles. Suitable materials for its manufacture will include selected types of acrylic, butadiene styrene and high-impact polystyrene.

This head H will correspond in shape to the end of the retainer R and it will carry the cannula C outstanding from its forward face 35 centered and adjacent to the bottom edge 27 as heretofore described. The two insert needles N will also outstand from the rearward face 36 at spaced locations, at the axis position of each passageway 24 when the head is connected to the retainer.

Other features include a passageway means within the head to connect the tubular cannula with each of the tubular insert needles and preferably, separate passageways 37 are formed within the head, each independent passageway 37 extending from the cannula to an insert needle so that the passageway through the tubular cannula may communicate with the similar passageway through the tubular insert needles, as hereinafter further described. The head includes further, a rearward hood 38 which overlies and extends about each side of the forward end of the retainer when the two members are interconnected. Each side of this hood carries a lug 39 which engages with a socket 31 on the corresponding side of the retainer to lock the two members together as clearly illustrated at FIG. 2 and heretofore described. To complete the head, a stop 40 outstands from the inner face 36 adjacent to the lug 39 which engages the socket 31 in strip 32, the stop 40 serving to limit the distance to which the strip 32 may be flexed when disconnecting the head from the retainer.

To facilitate the manufacture of this head H and especially the passageways 37 within it, the head is preferably formed as two comparatively flat wafers, a forward, outer wafer 41 and a rearward, inner wafer 42. These wafers join a contacting surfaces 43 and 43a and are welded together by any suitable method, such as by standard, thermal or solvent welding procedures to form a solid, unitary member.

The forward wafer 41 carries the hood 38 which extends rearwardly as a socketlike member to retain the rearward wafer 42. It is also formed with a boss 44 to securely hold the cannula C in position. The cannula, a small-diameter metal tube, is formed with a steeply sloped forward end 45 as a point for injection into a patients vein, the surface of the slope fac ing upwardly with respect to the wafer for proper positioning when being inserted into a patients vein. The base of the cannula extends through the wafer 41 as an inclined end 46 which projects from the contact face 43 in an upward direction to lie within the junction of the passageways 37, hereinafter further described. To complete this forward wafer 41, a lug 47 may project from the forward face at each side of the boss 44 to facilitate holding a protective sheath S, shown in broken lines at FIG. 3, which can maintain the cannula in a sterilized condition once it has been sterilized and ready for use.

The rearward wafer 42, which lies against the forward wafer 41 within the embrace of the hood 38, is formed with the passageways 37 at its contacting surface 43a as a channel having a V-shaped path with its apex at the bottom center of the wafer at the point where the cannula end 46 is located. Each branch of the channel extends outwardly and upwardly from this apex and to the base 48 of an insert needle N which is mounted in the rearward wafer 42 to outstand therefrom. Each insert needle N is held in position in the wafer 42 by a boss 49 projecting from the rearward surface 36 with the rearwardly extended end 50 being pointed to facilitate its insertion into a stopper. The base end 48 of each needle is also inclined and with the inclined face being directed towards the channel as in the manner illustrated at FIG. 10.

The use of this improved sampler is manifest from the foregoing description. A retainer R may be provided for repeated use while the cannula head H will ordinarily be provided as a throwaway item once it has been used, such assuring a completely sterile cannula for each patient and eliminating the chance of contamination of blood samples. To commence a blood-sampling operation, the head H is attached to the retainer R by fitting the lugs 39 into the retainer sockets 31. Two tubes T are then fitted into the retainer with the needles N being partially inserted into the stoppers 21 as illustrated at FIG. 2. Subsequently, the cannula of the sampler is inserted into a patients vein, and the tubes are then pushed into the retainer so that the needles N project through the stoppers and into the tube cavity to permit the blood samples to be drawn. The operation is completed by removal of the sampler from the patient, removal of the tubes from the sampler and finally, removal of the head from the retainer.

The tubes may be pushed upon their needles in a sequential manner or simultaneously, once the needles have been par tially inserted into the stoppers. Whenever, it is desirable to fill both tubes simultaneously, the pair of tubes may be carried in a common base 51 as indicated in broken lines at FIG. 2.

FIGS. 11 to 13 show a three-tube sampler similar in construction to the unit shown at FIGS. 1 to in that it is formed with a cuplike retainer R having a passageway 24 sufficient to accommodate three standard sample tubes, although the passageway 24' is illustrated at FIG. 12 as being a single passageway rather than a plurality of passageways as heretofore described. This retainer R is connected with a cannula head H at its front end and the sampler is formed as a rectangular unit in plan, generally oval in cross section with the underside 27 being arched and the top side 28 being crowned, as heretofore described. Other features of the retainer R are also similar. It includes rounded sidewalls 26, a limit line 29 for restricting the depth of insertion of sample tubes prior to using the sampler, and finger flanges 30' at the rearward end to facilitate holding the unit when the tubes T are being pushed into position for filling. The manner in which the cannula head H is attached to the retainer is modified, however, in that the retainer has sockets 31 spaced about its front edge to receive pins 39 on the head H as will be described.

The head H is also generally similar in construction to the two-tube head heretofore described, in that it is formed of two flat wafers 41 and 42 which are welded together when the unit is completed. The outer wafer 41 carries the cannula C in a boss 44 in the same manner heretofore described. The inner wafer 42 includes three passageways 37 which extend from a bottom apex where the cannula base is located, the three passageways, shown in broken lines at FIG. 12, extending to three insert needle bases 48'. This unit differs from that previously described in that the inner wafer 42' is smaller than the outer wafer and is centered upon the outer wafer to provide a rabbeted shoulder 52 whereover the forward end of the retainer R is fitted as best illustrated at FIG. I3. Lugs 39' upstand from this shoulder to fit into the sockets 31 to hold the retainer and head together. To connect or disconnect the head from the retainer, the rabbet edge 52 is cut back from its contact edge with the inner surface of the retainer as at sections 53 illustrated at FIG. 12. By squeezing the retainer, its top will be lifted as to the position indicated in the broken line 54 at FIG. 12, to release the lugs 39' from the sockets 31'.

The construction illustrated at FIG. 14 is a two-tube sampler constructed essentially the same as the unit described at FIGS. 1 to 10, excepting that a different mode for connecting the head to the retainer is provided. In this modified unit, hooks 55 are provided at each side 26" of the retainer R" to extend from the front end of the retainer and sockets 56 are formed at each side of the head H" to be engaged by the hooks to hold the head H" in position upon the retainer.

It becomes manifest that yet other constructions may be used to carry the cannula and the plurality ofinsert needles, in various head constructions or even in partial head constructions where portions of the head may be formed integrally with the retainer, and yet where the construction is not significantly modified from that disclosed herein. Therefore, while I have now described my invention in considerable detail, it is obvious that others skilled in the art can build and devise alternate and equivalent constructions which are clearly within the scope of the appended claims.

Iclaim:

l. A blood sampler adapted to receive a plurality of sample tubes of the type which are evacuated and have stoppers closing the ends thereof, and comprising:

a. a retainer, which is open at the rear end thereof, to receive said plurality of sample tubes, stopper first, at selected tube positions within the retainer;

b. a head traversing the front end of the retainer;

c. a cannula mounted upon the forward face of the head and extended forwardly therefrom;

d. a plurality of tubular insert needles mounted upon the rearward face of the head, extending rearwardly therefrom, and lying within the retainer, with a needle being located upon the head at the approximate center of each said selected tube position for contact with and insertion into the stopper ofa tube placed in the retainer at said selected tube position; and

e. a separate passageway within the head, independently interconnecting the cannula with each insert needle to permit the passage through the cannula to communicate with the passage through each insert needle, whereby blood will fiow through the cannula, when inserted into a patients vein, and into the plurality of sample tubes when they are placed in the retainer with the insert needles being inserted through the stoppers.

2. In the sampler defined in claim 1, wherein said retainer is formed as a flat unit, substantially rectangular in plan and oval in cross section, and being adapted to hold the tubes in a sideby-side arrangement.

3. In the sampler defined in claim 1, wherein said head is a separable member from the retainer member, and including further, a means adapted to attach the head onto the retainer when the sampler is being used,

4. In the sampler defined in claim 3, wherein the attaching means includes a hooklike lug on one member and a transversely disposed surface on the other member adapted to be engaged by the lug.

5. In the sampler defined in claim 3, wherein a portion of one member laps a portion of the other member, and wherein the attaching means includes a lug at the lapped portion of one member and a socket at the lapped portion of the other member adapted to receive the lug.

6. In the sampler defined in claim 5, wherein one of the members is resilient at the lapping, interlocking portions and is thereby adapted to flex to effect disengagement of the lug from the socket.

7. In the sampler defined in claim 3, wherein said head includes a hood lapping the retainer having diametrically opposed, inwardly directed lugs, wherein said retainer includes diametrically opposed sockets at its end adapted to be engaged by the lugs when the two members are interconnected, and wherein said retainer includes slits at each side of one socket of sufficient extent as to form an elastic strip which may be flexed sufficiently as to release the lug from the socket.

8. In the sampler defined in claim 3, wherein the head comprises a pair of flat wafers welded together as a unitary member, including a forward, outer wafer and a rearward, inner wafer, with the forward wafer carrying the cannula, with the rearward wafer carrying the insert needles and with said passageways being at the innerface of the two wafers.

9. In the sampler defined in claim 3, wherein the underside portion of the retainer is formed as an arched surface adapted to lie upon a patients arm and the cannula, mounted upon the head, is adjacent to this undersurface.

10. In the sampler defined in claim 9, wherein the walls of the retainer are sufficiently transparent as to view the stopper end of a tube inserted therein, and a mark on the walls of the retainer adapted to facilitate the partial insertion of a tube to the aforesaid selected depth.

11. A blood sampler adapted to receive a plurality of individual sample tubes, each of which is evacuated and is closed at its end by a comparatively thick rubber stopper, and comprising in combination therewith:

a. a retainer having a front end, a rear end, a flattened undersurface adapted to lie upon the body of a patient when a blood sample is being taken and a laterally widened socket cavity therein which opens at the rear end to receive said plurality of sample tubes stopper-first, in a longitudinal side-by-side array at selected positions therein, and with the floor portions of the socket cavity being adjacent to the flattened undersurface.

. a head traversing the front end of the retainer;

. a plurality of tubular insert needles having a length sufficient to penetrate the tube stoppers, with one needle for each tube, mounted upon, outstanding rearwardly from the rearward surface of the head, within the socket cavity and at each selected tube position, said needles lying in spaced parallelism to the cannula insert section and in a plane parallel with the aforesaid plane defined by the flattened undersurface of the retainer but above this plane and near the center of the head; and

e. a passageway means in the head communicating between each tubular needle and the cannula whereby, when each of the plurality of tubes is partially inserted into the retainer opening, to a selected depth, the stopper of each tube will contact a needle and the needles will be partially inserted into their stoppers to block off the passageway means to prevent a flow of blood from the cannula and through the needles whenever the cannula is inserted into a patients vein, but when one of the tubes is thereafter completely inserted into the retainer opening, the needle penetrates the stopper and the passageway means is open to the interior of the tube to permit blood to flow therein- [0.

12. In the sampler defined in claim 1 1, wherein the walls of the retainer are sufficiently transparent as to view the stopper end of a tube inserted therein; and

a mark on the walls of the retainer adapted to facilitate the partial insertion of a tube to the aforesaid selected depth,

13. In the sampler defined in claim 11, wherein the underside portion of the retainer is formed as an arched surface adapted to lie upon a patients arm and the cannula, mounted upon the head, is adjacent to this undersurface. 

1. A blood sampler adapted to receive a plurality of sample tubes of the type which are evacuated and have stoppers closing the ends thereof, and comprising: a. a retainer, which is open at the rear end thereof, to receive said plurality of sample tubes, stopper first, at selected tube positions within the retainer; b. a head traversing the front end of the retainer; c. a cannula mounted upon the forward face of the head and extended forwardly therefrom; d. a plurality of tubular insert needles mounted upon the rearward face of the head, extending rearwardly therefrom, and lying within the retainer, with a needle being located upon the head at the approximate center of each said selected tube position for contact with and insertion into the stopper of a tube placed in the retainer at said selected tube position; and e. a separate passageway within the head, independently interconnecting the cannula with each insert needle to permit the passage through the cannula to communicate with the passage through each insert needle, whereby blood will flow through the cannula, when inserted into a patient''s vein, And into the plurality of sample tubes when they are placed in the retainer with the insert needles being inserted through the stoppers.
 2. In the sampler defined in claim 1, wherein said retainer is formed as a flat unit, substantially rectangular in plan and oval in cross section, and being adapted to hold the tubes in a side-by-side arrangement.
 3. In the sampler defined in claim 1, wherein said head is a separable member from the retainer member, and including further, a means adapted to attach the head onto the retainer when the sampler is being used.
 4. In the sampler defined in claim 3, wherein the attaching means includes a hooklike lug on one member and a transversely disposed surface on the other member adapted to be engaged by the lug.
 5. In the sampler defined in claim 3, wherein a portion of one member laps a portion of the other member, and wherein the attaching means includes a lug at the lapped portion of one member and a socket at the lapped portion of the other member adapted to receive the lug.
 6. In the sampler defined in claim 5, wherein one of the members is resilient at the lapping, interlocking portions and is thereby adapted to flex to effect disengagement of the lug from the socket.
 7. In the sampler defined in claim 3, wherein said head includes a hood lapping the retainer having diametrically opposed, inwardly directed lugs, wherein said retainer includes diametrically opposed sockets at its end adapted to be engaged by the lugs when the two members are interconnected, and wherein said retainer includes slits at each side of one socket of sufficient extent as to form an elastic strip which may be flexed sufficiently as to release the lug from the socket.
 8. In the sampler defined in claim 3, wherein the head comprises a pair of flat wafers welded together as a unitary member, including a forward, outer wafer and a rearward, inner wafer, with the forward wafer carrying the cannula, with the rearward wafer carrying the insert needles and with said passageways being at the innerface of the two wafers.
 9. In the sampler defined in claim 3, wherein the underside portion of the retainer is formed as an arched surface adapted to lie upon a patient''s arm and the cannula, mounted upon the head, is adjacent to this undersurface.
 10. In the sampler defined in claim 9, wherein the walls of the retainer are sufficiently transparent as to view the stopper end of a tube inserted therein, and a mark on the walls of the retainer adapted to facilitate the partial insertion of a tube to the aforesaid selected depth.
 11. A blood sampler adapted to receive a plurality of individual sample tubes, each of which is evacuated and is closed at its end by a comparatively thick rubber stopper, and comprising in combination therewith: a. a retainer having a front end, a rear end, a flattened undersurface adapted to lie upon the body of a patient when a blood sample is being taken and a laterally widened socket cavity therein which opens at the rear end to receive said plurality of sample tubes stopper-first, in a longitudinal side-by-side array at selected positions therein, and with the floor portions of the socket cavity being adjacent to the flattened undersurface. b. a head traversing the front end of the retainer; c. a cannula having an insert section adapted to be inserted into the vein of a patient, mounted upon, outstanding forwardly from the forward face of the head and positioned at the approximate lateral center of the head but being offset to the bottom edge of the head with the insert portion being substantially parallel with and lying closely adjacent to a plane which is generally defined by the flattened undersurface of the retainer; d. a plurality of tubular insert needles having a length sufficient to penetrate the tube stoppers, with one needle for each tube, mounted upon, outstanding rearwardly from the rearward surface of the head, within the socket cavity and at each selected tube position, said nEedles lying in spaced parallelism to the cannula insert section and in a plane parallel with the aforesaid plane defined by the flattened undersurface of the retainer but above this plane and near the center of the head; and e. a passageway means in the head communicating between each tubular needle and the cannula whereby, when each of the plurality of tubes is partially inserted into the retainer opening, to a selected depth, the stopper of each tube will contact a needle and the needles will be partially inserted into their stoppers to block off the passageway means to prevent a flow of blood from the cannula and through the needles whenever the cannula is inserted into a patient''s vein, but when one of the tubes is thereafter completely inserted into the retainer opening, the needle penetrates the stopper and the passageway means is open to the interior of the tube to permit blood to flow thereinto.
 12. In the sampler defined in claim 11, wherein the walls of the retainer are sufficiently transparent as to view the stopper end of a tube inserted therein; and a mark on the walls of the retainer adapted to facilitate the partial insertion of a tube to the aforesaid selected depth.
 13. In the sampler defined in claim 11, wherein the underside portion of the retainer is formed as an arched surface adapted to lie upon a patient''s arm and the cannula, mounted upon the head, is adjacent to this undersurface. 